Field of the Invention
The invention relates in general to automatic manufacturing and in particular to a new and useful method and a device for automatically joining and machining assemblies and components thereof.
It is known from DE-OS No. 28 10 822 to preposition, in a first station of a transfer line for automobile body welding, several sheet metal elements forming a subassembly on a pallet and to clamp them preliminarily in this conjugate position. The pallet with the loosely assembled body assembly then arrives in a fixing station which, in addition to welding robots, also has side frames with chucking devices engaging the various body parts to fix their final geometry. The body parts are subsequently tacked in this position by spot welding. From this so called fixing station the pallet with the tacked body assembly gets to a next machining station in which the body is finish-welded, using appropriate centering and chucking means.
In order to be able to process in such a transfer line different subassemblies, e.g. a 2-door or a 4-door body type of a vehicle, several side frames with permanently set-up chucking devices fitting the respective body type are provided in the fixing station. In the simple case, there are provided in the fixing station itself two different kinds of side frames which can be put into waiting positions when not being used. But it is also possible to have a greater number of side frames in readiness via a conveyor and a storage facility and feed them in when needed. This publication further provides for making one side frame suitable for two similar types of body assemblies in that the chucking devices for both types are mounted to the side frame and the chucking devices needed for the respective type are then actuated selectively.
Freely programmable welding robots are provided for the welding operations which can be programmed by software to the various assembly types.
On the one hand, the known transfer line has the disadvantage of a relatively poor operating reliability due to the series arrangement of the various work stations. If one station in the line fails, all other succeeding station are also stopped.
On the other hand, the hardware sophistication for the flexibility of the transfer line is great. A separate set of side frames with their own chucking devices is required for each body type. Due to the fixing station for tacking, and the machining station for finish welding, being separated from each other, the costs for chucking devices is doubled. In addition, in the simple embodiment, the fixing station is flexible to a limited degree only. If the flexibility is to be improved, a space and cost intensive conveyor and a storage facility are required.